Seems to work smooth, although the same issues still apply as with the Windows version of pureplera1n - namely WinterBoard not working.

Here's how to use the tool:

Go to purplera1n.com, and click the Mac logo to download the tool. Make sure your iPhone 3GS is connected to your computer.

Unzip the program if your browser didn't already for you, and double-click the purplera1n icon to launch the app.

(Note: this is Intel only. PPC folks will be greeted with this pretty message: )

Press the button that says Make it ra1n!

purplera1n will let you know its waiting for your iPhone. The iPhone will go into recovery mode while this is happening.

You'll see the modest geohot's image on your iPhone.

Assuming all goes well, within a minute or two you should see the Done! Wait... message in purplera1n.

After the iPhone boots, it will have a new app called Freeze with a white icon.

Open Freeze and tap 'Install Cydia'. It will now download and install the package and then clean the installation. Wait till it says 'Finished!' and then just exit to home screen. If you still don't have cydia, reboot the phone and use freeze again.